C17 H31 COOH is formula of:

In case of a saturated fatty acid, number of hydrogens are double the number of carbons. In this fatty acid, number of carbons are 18. Number of hydrogens are 32. In case of saturated fatty acid, if carbons are 18, then Hydrogen must be 36 (double). So there is loss of 4 H (means 2 double bonds). So, this is Linoleic acid (18 C, 2 double bonds). WITH REGARDS TO OTHER OPTIONS refer table below: OMEGA 3 OMEGA 6 CERVONIC ACID/DHA - 22 Carbons & 6 Double Bonds GAMMA-LINOLENIC ACID- 18 Carbons & 3 Double Bonds ALPHA-LINOLENIC ACID- 18 Carbons & 3 Double Bonds LINOLEIC ACID- 18 Carbons & 2 Double Bonds TIMNODONIC ACID- 20 Carbons & 5 Double Bonds ARACHIDONIC ACID- 20 Carbons & 4 Double Bonds